<?xml version='1.0' encoding='UTF-8'?><xml><records><record><source-app name="HighWire" version="7.x">Drupal-HighWire</source-app><ref-type name="Journal Article">17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Retter, Talia L.</style></author><author><style face="normal" font="default" size="100%">Schiltz, Christine</style></author></authors><secondary-authors></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Visual Stimulation Under 4 Hz, Not at 10 Hz, Generates the Highest-Amplitude Frequency-Tagged Responses of the Human Brain: Understanding the Effect of Stimulation Frequency</style></title><secondary-title><style face="normal" font="default" size="100%">eneuro</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2025</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2025-06-01 00:00:00</style></date></pub-dates></dates><elocation-id><style  face="normal" font="default" size="100%">ENEURO.0426-24.2025</style></elocation-id><doi><style  face="normal" font="default" size="100%">10.1523/ENEURO.0426-24.2025</style></doi><volume><style face="normal" font="default" size="100%">12</style></volume><issue><style face="normal" font="default" size="100%">6</style></issue><abstract><style  face="normal" font="default" size="100%">In frequency tagging, visual stimulation at a frequency (F) of ∼10 Hz has long been known to generate the highest-amplitude response at F in the frequency domain over the human occipital cortex with electroencephalogram and other high temporal-resolution methods. Brain responses are indeed commonly assessed simply at F (i.e., the first harmonic = 1F), under the assumption that the response is represented at a single frequency, i.e., “steady-state” or approximately sinusoidal in terms of amplitude over time. This condition is met at stimulus presentation frequencies above ∼4–8 Hz in the visual modality; consequently, frequency tagging has often been limited to F above this “floor.” Here, we support a less-common perspective, that frequency-tagged responses do not need to be steady-state, such that slower F are valid. In this case, it has been shown that is not appropriate to measure nonsinusoidal responses at only F but that nonsinusoidal responses can still be analyzed simply and advantageously in the frequency domain through baseline-corrected amplitude summation across harmonics (F + 2F + 3F… = Fs). Critically, we demonstrate that although the highest-amplitude F response occurs at F = 10 Hz, the highest-amplitude Fs response occurs at approximately F &lt; 4 Hz. We use this example toward understanding the effect of stimulation frequency on response amplitude and discuss its caveats and limitations. We address what defines an “optimal” stimulation frequency (note: it may not always be the F yielding the highest-amplitude response) and reflect on considerations when choosing a stimulation frequency in different contexts.</style></abstract></record></records></xml>